Method of drying paper in the form of a continuous web



E. A. OHLIN Nov. 3,1931.

I METHOD OF DRYING PAPER IN THE FORM OF A CONTINUOUS WEB Filed Feb. 23. 1928 I INVEN TOR. Erik fl.

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Patented Nov. 3, 1931 UNITED STATES PATENT OFFICE ERIK ALEXANDER 6ELIN, OF HYLTEBRUK, QWEDEK METHOD OI DRYING PAPER IN THE FORM OF A CONTINUOUS WEB Application filed February 23, 1928, Serial No. 256,408, and in Sweden February 28, 1827.

The present invention relates to such methods for drying paper and the like in the form of continuous webs, where the paper passes over one or more heated drying rolls and an is caused to pass over the outer surfacevof the paper we In the methods of the kind referred to used Y give the desired result; Finally, the methods used up till now suffer from the drawback that they are uneconomical because they need a considerably larger supply of heat than ought to be necessary to obtain the dryness wanted.

.The present invention has for its object a method which overcomes these difiiculties, and by means of which the paper is uniformly dried, and whereby the degree of dryness can be regulatedin a convenient and precise manner so that the paper when dried retains the moisture which may be desired in the partic-' Further, this method implies a ular case. considerable saving of heat compared with methods hitherto used. a v In order to obtain this result the drying air is, according to the present invention, preheated to a comparatively high temperature andconducted over the paper web in the same direction as the direction of movement of the web.

The invention has also for its object to provide means for carrying out the process, and in the acompanying drawings it is shown by way of example a paper making machinery of so called Yankee-type fitted in accordance with the invention.

In the drawings Figure 1 is a diagrammatic side view of the press and drying section of the machinery,

Figure 2 is a side view on a larger scale of the upper portion of the mantle,

the drying cylinder or roll of the machine with the mantle surrounding the drying cylinder partly in section,

Figure 3 is a longitudinal section through Figure 4 is a top plan view on a smaller scale of the'mantle, and

. Figure 5 is a diagrammatic view, showing how the device is connected to a steam generator for heating of the drying cylinder and to a preheater for the drying air.

In the drawings A denotes the frame-work of the machinery, which carries the shaft 2 of the hollow drying cylinder 1, said cylinder being in 'a known manner heated by means of steam conducted to the interior of thecylinder. The upper portion of the cylinder 1 is surrounded by a mantle 3 having the form of a section of a hollow cylinder and provided with double walls 4 and 5 respectively, the inner one 4 of which being disposed at a little distance from the surface of the drying cylinder so as to form an interspace 6 serving as a drying chamber for the paper web 7 passing around the cylinder. The mantle 3 is surrounded by a plate cover 8, under which there is applied a suitable heat-insulating material 9. In order'to limit the drying chamber 6 at its sides there is, to each edge of the mantle 3, fixed a flat arc-shaped member 10 of a flexso ible material which is tightly pressed against the end surfaces of the drying cylinder by means of a number of springs 11 (see Figure 3). At each end of the drying chamber 6, r e. g. where the paper web enters into and leaves same, there is provided a rotatably mounted-roll 12 which keeps the web pressed against the drying cylinder and against the sides of which the ends of the members 10 are pressed. The necessary tightness between the mantle 3 and the rolls is obtained by means of plates 13 or the like which are connected to the mantle and made to slide against the rolls, springs 14 being provided to keep the plates pressed against the surface of the rolls. By means of the tightening devices now described the drying chamber 6 will be quite closed so that leakage does not occur even if there should be some difference between the pressure inside the drying chamber and the atmospheric pressure.

' the mantle may suitably be provided with transverse projections 15, so as to cause the air to turbulate and to force the same in contact with alternatively the web and the inner wall of the mantle. In order to obtain an equal distribution of the air over the whole width of the web the supply pipe 16 -for the hot-air is connected to the drying chamber by means of afunnel-shaped piece 17, as

clearly appears in Figure 4, the discharge pipe 18 for the air being connected to the dry ing chamber by means of a similar'piece 19.

lhe air supplied to the drying chamber may suitably be pro-heated to about the same temperature as that of the air leaving the chamber. As shown in Figure 5 the preheatof the air may conveniently be efiected in a preheater 20 of a known construction, P

through which fresh air is causedto' pass, and in which the moist air escaping fromthe drying chamber may deliver part of its heat before being, in the usual manner, used for the heating of the factory buildings or similar purposes.

For heating. of the mantle 3 the condensate from the interior of the drying cylinder may suitably be used, the condensate being by means of a pipe (21 in Figure 5) conducted to the one end of the space between the walls 4 and 5. After having passed through this space the water, through a pipe 22 connected to the other end of the mantle, is conducted back to the s eam generator 23 which through a pipe 25 delivers fresh steam to the drying cylinder.

Bv the method described above. it is evidently possible to vary the degree of moisture of: the dried paper simply by regulating the quantity of the supplied drying air and the temperature of same, as the capacity of the paper of absorbing and keeping moisture varies with the pressure of the steam in the drying chamber and with the degree of super-. heating of the steam. 7

Thus, the wanted degree of wetness of the dried paper is obtaned by adjusting the supply of the drying air and its'temperature in such a manner, that the drying air in that considerably preheated there is .no need for supplyin the same further heat in the drying chem er but the heat emitted by .the drying cylinder can. be entirely utilized for.

evaporating the water in the paper web. B

using the water condensed in the dryin cy inder for heatin the mantle it is eilecte that the inner wall 0 the same is given a tem erature higher than that in the drying cham er.

Such parts of the evaporated steam that come into contact with the said wall will be superheated, and the steam thus superheated isby means of the transverse projections 15 brought into contact with the moist pa er web, whereby the steam is saturated. In t is manner part of the drying work is efiected b the mantle. Byheating the mantle this a vantage is also attained that condensation upon and water dropping from the inner surface of the mantle is prevented.

The invention is not limited to the embodiment described and shown, but may be varied in details without departing from the spirit of it.

What I claim is I 1. The method of drying paper or the like comprising, passing a continuous web over heated drying surfaces through a drying space surrounding said surfaces, directing to the end of the path of the web and in the samedirection as the direction of movement of the latter, pie-heating the air passed throughthe space to substantially the same temperature as that of the air escaping therefrom, circulating a heated fluid through a chamber above said drying space, and preheating said fluid to a higher temperature than that of the air directed throughout said drying space.

2. The method of drying paper or the like comprising, passing a continuous web over heated drying surfaces through a drying.

space surrounding said surfaces, directing pre-heated air throughout said drying space to the end of the path of the web and in the same direction as the direction of movement of the latter, pre-heating the air passed through the space at substantially the same temperature as that of the air escaping therefrom, heating the drying surfaces by means of steam, and conducting the condensate from the steam used in heating said dr 'ng surfaces through a chamber above sai space to heat the air directed throughout the latter.

In witness whereof I have hereunto set my hand.

ERIK ALEXANDER (lHI IN.

part of the drying chamber where the web leaves the-same will be in such a state that the paper can not be dried above the desired a degree of dryness Owing to the fact that the air is re-heated air throughout said drying space. 

